1. Field of the Invention
The present invention relates to a semiconductor device manufacturing apparatus, and more suitably applied to a bias sputtering apparatus for performing thin film sputtering process and etching process simultaneously.
2. Description of the Prior Art
Manufacturing apparatuses of various kinds are now being used to form semiconductor devices on a semiconductor wafer. As one of these apparatuses, a bias sputtering apparatus is known. This bias sputtering apparatus has been developed to improve an insufficient step coverage at the stepped (profile) portions of deposited films formed in accordance with the ordinary sputtering process. The primary object of use of this bias sputtering apparatus is to planarize the thin films.
In this bias sputtering apparatus, a planar magnetron or a diode cathode is used to apply a bias voltage to the semiconductor substrate. In the case of planar magnetron, two matching boxes are arranged on the upper and lower sides of a reaction vessel. The two matching boxes are connected to a high frequency power source. That is, the two matching boxes are connected to two amplifiers separately, and further connected to an exciter (13.56 Mhz) in common.
Within the reaction vessel, the support base is rotatably attached to an axle electrically connected to the lower matching box. The support base is placed within the reaction vessel. The holder plate is mounted on the support base, and the semiconductor wafer to be processed is placed on the holder plate.
Further, within the reaction vessel, a flat target electrode (an anode) composed of a planar magnetron is provided and is electrically connected to the upper matching box. A plurality of annular magnets are further arranged within the reaction vessel, in contact with the reverse side of the flat target electrode.
Further, within the reaction vessel, a water cooling mechanism and a shield electrode are both provided. In this bias sputtering apparatus, the semiconductor wafer to be processed is mounted on the holder plate (which functions as a cathode) being kept a predetermined distance away from the flat target electrode (which functions as an anode).
When a voltage of several hundred volts is applied between the target electrode (anode) and the holder plate (cathode) for electric discharge, the lines of magnetic force generated from the magnets go out of the surface of the target electrode and come to the surface of the same target electrode again in such a way that the magnetic force lines surround the surface of the flat target electrode. Therefore, electrons are ionized by the discharge and moved as with the case of a magnetron at the intersectional portions between the magnetic field and the electric field, so that a high density plasma can be generated.
In the bias sputtering apparatus as described above, since the film deposition process and the etching process both progress simultaneously, and further since high frequency power is applied between the holder plate (which functions as a cathode) and the target electrode (which functions as an anode), a film deposited on the semiconductor wafer grows and simultaneously the re-sputtering occurs from the bottom of the stepped portions formed on the semiconductor wafer to the side walls or the corner portions of the semiconductor wafer, so that all over the surface of the semiconductor wafer can be planarized.
Accordingly, this bias sputtering apparatus can be adopted not only to form a metallic wiring film but also to form an interlayer insulating film for a multi-wiring layer and a multilayer (three or more) wiring layer itself.
FIG. 1 is a cross-sectional view showing the support base 2 placed within the reaction vessel (not shown) of the bias sputtering apparatus. FIG. 2 is an enlarged cross-sectional view of FIG. 1. On this support base 2, an alumina holder plate 3 is mounted, and further a semiconductor wafer 1 to be processed is mounted on the alumina holder plate 3. Further, a heating source (not shown) is provided just under the support base 2 to heat the semiconductor wafer 1 to be processed up to a predetermined temperature.
In the bias sputtering apparatus as described above, the holer plate 3 for holding the semiconductor wafer 1 is functioned as a cathode. Further, the size of the holder plate 3 is usually determined to be relatively large to suppress the dispersion in the etching process performed simultaneously with the thin film sputtering process.
FIG. 2 shows the status where the semiconductor wafer 1 to be processes is covered with a deposited film 4. In this case, however, since the dimensions of the alumina holder plate 3 for holding the semiconductor wafer 1 is determined to be larger than that of the semiconductor wafer 1 to be processed, not only the semiconductor wafer 1 but also the holder plate 3 are inevitably covered with the deposited film 4.
On the other hand, in the bias sputtering apparatus as described above, since the thin film is deposited all over the semiconductor wafer 1 to be processed and in addition on the holder plate 3, in case cracks are produced at the end portions of the deposited thin films when the processed semiconductor wafers are being conveyed, there arises a problem in that micro-particles inside the thin film are scattered onto the wafer surface as dust, thus deteriorating the characteristics of the semiconductor devices.